Major examples of an ophthalmologic image sensing apparatus are a scanning laser ophthalmoscope (SLO) and an optical coherence tomography (OCT) apparatus. Major examples of the OCT are a Time Domain OCT (TD-OCT) and a Spectral Domain OCT (SD-OCT).
In order to improve the resolution of a fundus image of an eye to be inspected, an attempt has been made to increase NA of a light projection system for the eye to be inspected. Measuring light projected to the fundus passes through optical tissues of the eye to be inspected, such as a cornea and a crystalline lens, and is affected by aberrations of the optical tissues. When the aberrations are large, there is a case where the quality of the fundus image is not improved by the increase in NA.
In view of the above, NPL 1 discloses an adaptive optics OCT (AO-OCT) which incorporates into the OCT an adaptive optics (AO) system in which aberration measurement and aberration compensation are repeated at high speed to pre-compensate for an aberration of the measuring light, which is caused in the irradiated eye to be inspected, based on a measured aberration.
In the AO-OCT, aberration of light obtained by dividing a return beam from the eye to be inspected is measured. Therefore, an intensity of the return beam to be used for the fundus image reduces, and hence the quality of the fundus image degrades. Even when the intensity of light entering the eye to be inspected is increased in advance to compensate for the reduction in intensity of the return beam which is caused by the division, there is a limit because the intensity of the incident light is limited in under safety standards. Thus, it is necessary to minimize the intensity of the light obtained by dividing the return beam for aberration measurement. On the other hand, in order to perform aberration compensation in short time, short-time aberration measurement is required. Therefore, it is necessary to maximize the intensity of light for aberration compensation.